Reversible lubricating grease composition



Patented Apr. 18, 1950 castes;

REVERSIBLE LUBRICATING GREASE COMPO SITIO-N Alillflid Js Morway,- Clark,and John cmzimmer,

Union, .N. 1., .assignors to Standard;

DgYBlOP a mentrCompana, a orpor tion. of. De aware N oDi-awingwApplication September 32031947; Serial-No. 77553103 The epresen-teiiwention-relates;tonalreversible.t

position-although fundamentally; they consist .of

soap; mixed-swith. ordinaryalubricating oil-.1 Both: that oilaandethetype andequantity e01 soap nmay be widely variedatomeet theacomiitions-of. a are ticular r lubrication zp roblern ,requiring theuseof as semiefluido lubricants- Thee lubrication prob-, lems towhichthegreaselcompositions are-applied: are-:2 almost 1- as, numerous..- asthe compositions: themselves. Oneetroublesomesproblem =presents itself-.witla-- the. attempttto .-lubrioate bearings on: v t ttemperaturessin,,thee neighborhood;- of, theeboiling; point-.01. ,water;and, often above andespeciallv-those rhearings which; operate-at tomeperatures tbetweenslimw 2x11113001 Fa" in the re eneeeofi waters.Gneasessfor;the most part. are-a1 either dispersions on; solutions, or;metallic. soaps: insaa-minerahmbricating oiLwhich willrangeeinsviscosity from 60s seconds Saybolt at 100 F. for the light oilstoe-about ififluseconds; .Eiaylaoltsat-4100 F) for;theebrightsstockssThe soaps ordinariiy usedavforrthermaking of greases consistbtithewa1ka1inmetaL-:SOapS,- alkal-inmeartn, soaps k or. mixturesthereonz, Sometimes special soaps suchraszaluminumssoaps are-remplo-yed.Intheapreparationnotithe soaps am excess of themetal 1 is sometimes;employed which 1results= in the production of a basic soap. ln-tthelubricae tiomoixbearingsoperating attempemturesaboi e 140 ithevordinarytypengrleaseslaretfound to haveemany imperfectionsm For instancethellinel soap.greases..requixevtha.presencevor in orporatetiionaonagsmall amount .;0;Wa e1= athe compmw sitionltosecureetnevgreaserlike struaturel When. temperatures ,around. 2123]Bears obt ineds ha water present sin a ,lime ,so pr liease evaporates.

andvlthe limejsoap, which is ,insolublein the, .oil F 6:01am. ((31. zszssz:

theapresence of water they are s onidissolved outs and ,removed f1 Om..the -bearing, W-ithuthe re;v moslalgof.,theesoam which Junctions.-to-hold the oil,,-the .oilt isnolonger retained inthe bearing Itvhas:,.p 1 :eviousl; z -been =suggested thatagreasess might. bevpreparedsfrom bariumesoapss y In; gthes- Prior. art, however,difiicu1ty ,has, been; encoun teredr.sin"pteparing.stableesoapseor-,barium-.baSQs nd it has.be n he1.d sen.era11v hat onlythabasios bariumsoaps, i. ,e-kthose; containing-an excess-otbariumlhydroxide, couldabe -g used-Vito prepare;

reases... Basic 4 barium, soap; reases; althoughe possessingarelativelyhigh meltingipointsgofteng reachinaaslhi h aseooz depend n -u on h eamount and kindofnbasiczbarium soap; presentingv theoillosetheir-greasestructurewhensubiectggk tovtempelfatures ins theaneighborhood? of th eini melting pointsand revertvtoaa:mixturemfistnatim fled oillandz soap. Afterlthe melting-:point-mfwas invention includes "as" one aspect a method of preparingvamechanically stable grease having the otherwise desirable propertiesofbariumbasegreases-without using an excess of the barium' c oxide orhydroxide witlrit's accompanying disad-f 4 vantages:

Mixed alkaline earth soapgreases suchas are calcium-barium greasespossess the faults of? bbth lime soap greases and the basic bariumsoap;greases. Aluminum soap greases although often" used in life-timebearings, tend to emulsify with water or become sem-ifi'uid and rubberyatele= vated temperatures,- such as above 140 F: and-Tor; these=reasonscannotbe retainedin a bearing;v operatingmnder such conditions; Sincethe re tention of fluid oil in a bearing ofiers mechanical? problems, itisapparent that the greases asabpve; described are notparticularlvadaptable to ,th eg lubrication of life time"bearings land that anirhproved grease devoid of-theseimperfectionsjsv especially desirable,

The. principal object of j this invention is the v en 1 1 a bari m sansrea epf excellent tructures eesyo o.preparaaml which ssrev rsihle'ewa nres s udl hermellxjstebl ese andotherxoblectsa nts ianssa nt andmecha icall will be apparent to those skilled in the art upon readingthe following description.

A further object of this invention is to compound barium soap greases ina manner which avoids the introduction of objectionable ingredientswhich appear to have given rise to diificulties encountered in prior artattempts to prepare barium base greases.

It has now been discovered that greases compounded of neutral and/oracid barium soaps and mineral lubricating oils produce greases which arewater insoluble, transparent, mechanically and thermally stable andreversible, provided certain procedures are observed during theirpreparation. These greases can be used at any temperature up to 212 F.in the presence of water without decomposition and at. temperaturesabove the boiling point of water, not to exceed the ignition ordecomposition temperature of the constituents themselves, and may beliquefied and solidified innumerable times without the loss oflubricating quality or grease structure.

' It appears that two special procedures are desirable in thepreparation of mechanically stable barium greases having theotherdesirable properties mentioned above. In the first place it appearsto be desirable to avoid the introduction of barium carbonate when thebarium oxide or hydroxide is used as a saponifying agent. Apparentlycommercial barium oxide. or hydroxide, tends to react with carbondioxide in the air over a period of time to revert to the somewhat morestable carbonate. If, a barium oxide which includes an appreciablequantity of the carbonate is employed in forming the grease, or informing. the soa to be incorporated in grease. the diffic'ulties knownto the prior art'in securing proper grease structure, mechanicalstabilty, reversibility. etc., appear to arise. Hence it is desirableto'use either a freshly calcined barium oxide (or freshly hydrated oxidewhich has been kept away from the air since calcination) or to keep thecalcined barium oxide in an inert atmosphere, for example in a nitrogenatmosphere, after cal cination.

A further requisite which appears to be quite essential to securing agood stable, reversible grease'structure, appears to be the formation ofthe soap. or the saponification of fatty material, direc ly in themineral oil which is to serve as the liquid lubricating element of thefinished grease com osition. The use of preformed soap has been found tobe unsatisfactory and in fact it is commonly impossible to secure agrease structure at all when it is attempted to incorporate' a reformedbarium soap into lubricating oil. This is particularly true with respectto the basic barium soaps used in the prior art. g

1y calcined by heating barium carbonate, or the impure oxide, to asufiicient temperature to drive off the carbon dioxide. Barium carbonateis not easily decomposed but the calcination appears 4 to be facilitatedby the addition of a small amount of carbon such as charcoal, carbonblack or other carbonaceous materials, with heating to a fairly hightemperature. In the absence of carbon or carbonaceous materials, it maybe necessary to heat the carbonate to a temperature as high as 1350 C.if heating is carried out under atmospheric pressure. By using reducedpressures, and/or an atmosphere free from carbon dioxide, thetemperature may be somewhat lower. In any case heating is carried out ata sufficiently elevated temperature and over a period sufiicientlyextended to decompose substantially all of the carbonate and obtain asubstantially pure oxide. Assuggested above, if the calcined oxide isnot to be used promptly, it should be protected from access to air,preferably by storing it in a nitrogen atmosphere.

The barium oxide, preferably substantially free from the carbonate asmentioned above, may be hydrated to the hydroxide, preferably in aninert medium suchasoil, before adding the fatty maaqueous slurry to thesoap stock in mineral oil solution. However, a fairly. pure commercialbarium hydroxide appears to be satisfactory although it is preferred touse the freshly hydrated oxide. Conventional methods forgrease'manufacture may be employed with the exception and the addedadvantage that after the soaps are completely formed and dispersed inthe mineral oil the grease may be placed in final package containers andpermitted to cool without the necessity of further working.

Preferably, the soap stock or fatty material is first dissolved bystirring it into at least a portion and preferably all of thelubricating oil, accompanied by heating, if necessary, to a temperatureat least equal to the melting point of the soap stock. Thereafter, for aneutral soap grease the stoichiometrical proportions of hydrated bariumoxide are added, or slightly less if an acid grease is desired. Duringthe formation of the soap, the ingredients are heated. moderately, e.g., to a temperature around 200 F.v

erably may be the final shipping containers toavoid further handling.

The total amount of soap in the grease made in accordance with thisinvention will range from about 5% to about 50% by weight based upon thetotal grease composition depending upon the properties desired in thefinished grease, the:

type and viscosity of the oil used and the character of the fat or acidemployed in the produc tion of the soap. Y

Although a wide range of lubricating oils may be employed as thelubricant in the grease, in general the base oil comprises an oil havinga S. U. V. in the range of from about 35 to 220 seconds at 210 F.However, forthe production of most greases of the type contemplated bythis;

invention it is preferred to use a base oil having a viscosity of fromto 2400 at 100 F.

The usual types of soap stocks, such as animal or vegetable fats orcommercial stearic, palmitic,

and oleic acids, as well as fatty acids split from hydrogenated fatssuch as hydrogenated fish oil acids, which soap stocks contain at least12 car,-' bon atoms to the molecule, usually 12 to 22 or 24oarborratornsr may 'fie used' for tiie production of tlie soaps' usenitfor'the -purposes of tiii's" ira/en tion: Other-additives such as antioxidants," ad liesives and rust preventing agents may' be" incorpoiattachwitldvsmt departing 'from tlie scope oi' use invention. 7

The" fdilowing exanmlswill I serveasfiliustra tionsoftypicalcompositionsaccordiiigfi to'this in ventinr- 10.00 %;by; weight .commercialoleic.acid- 8.0!? byyweight i barium hydroxidee eil mixtu-re 81.93 by;weighttlubricating oils (1cw.;cold..test

coastal ltypeioil) BSA/ m; (retainedbarium o xi'dg. 332 91,?

The oleiciacid'ian'dethechomogeneoustemulsiorr Exampte z iA'hardergrease was prepared'b'y' the samegen' eral methodasitl'iatiirrrEiiamplesli using the following.,. ingredients-Percentages 1 given are .by weight;v as in Eiiampll. 1'.

znifaicommer'cialioleici acids l95/5i-bazriuicd'il'l'ydrcside on1mixturv61%.1lubricatingroi1 i( lowa'colrl .tc'st coastal) 1 28.5%calcined"bari1im" oxid; 2835 70" Water, 4320 7 0 lubricating o Anexcellent hard grease resulted which ran for 1 hour in the AnnularBearing Engineers Committee test machine at temperatures above 230 F,with no leakage and with good lubrication. The grease showed sometendency to ball up and to become somewhat brittle at temperatures above200 F. This grease, which con tains less mineral oil than that ofExample 1, appears to be particularly suitable Where a hard grease isneeded for service at moderate temperatures.

Example 3 The grease of Example 2 was modified by incorporatingadditional 011 and a small amount of an aluminum soap. Thus 2 grams ofaluminum stearate were slurried with 48 grams of mineral lubricating oiland the slurry was added to 200 grams of the grease. The mixture washeated to the melting point and thereafter cooled slowly. An excellentproduct of homogeneous structure was obtained.

Example 4 20.00% hydrogenated fish oil acids 19.00% barium hydroxide-oilmixture 1 61.00% low cold test coastal type lubricating oil 28.5%calcined barium oxide, 28.5% Water, 43.0%

lubricating oil.

The grease was made according to the procedure outlined in Example 1above, resulting in a product having a penetration of 265/280 at 77 F.and a melting point of 250 F. The charone" However: when again cooledto-be1ow the 'boilin'gF point of water thegrease will turn to asmoothlromogenecusflubricantf- With reference=--to-the bariumcompounds,- it appears" that trie calcined bariurn' oxide is more-active"than" commercial "b arium hydroxide, probamy because of the presence ofperceptiblequantitis of bariumcarb'o'nate in the latterr For this"reason i it is preferred-" to hydrate? the oxid'e freslily' irrthe"absence of carbon dioxid' a The" hydraticrr' oil, as suggested 1 above;convenient way to 1 exclu'dcarbon dioxide but there-"are various otherwaysof excludingit: as will be"-apparent to*those skilled ifith'e a-r Itappears-to bedesirableto "use an excess' of watihydrating and;as-=indicatedfabovei there suiting soap is preferably neutralorsiightly-acidifeapHatleastas low'as 7.0. 7

The expr'essiorr consisting essentiallyfias used er the claims;meansthat the composition is up-substantiauy entirel of"theingredintsrecited. and that such irigredintsmre==tlie=niaiff ones' an'd tnosewnich characterize tiie compesition; This does-'notexcludeminorcuantitis ofother" conventional ingredients? are rela irtsuchsmall. quantities that"th'e essentia'l' prop erties of the comp osition"are substantially u -1- affected.

While specific procedures and tem eratures havdbeenrecite'd intheforegoing*'examp1es;.it will he? understood that these may be variedsomewhat? Slow cooling. of the" barium greases appears to beessen'tial:hence-the process *is-znot as"satisfactorilyfconducted with fast'coolingfcoii tiriuou's" process apparatus." Citherwisefthe" com tinnousroeesv appears some applicable: Iir general the barium soaps "willcomprise prefer ably from 15 to about by weight of the greases, butgreases having soap content of 5 to may be prepared satisfactori1y. Theaddition of a small amount of aluminum 'soap, e. g. aluminum stearate,tends to make a smoother and more homogeneous product. The alum num soapis preferably employed in proportions of 0.2 to 4% by weight, based onthe total composition, but very satisfactory grease may be preparedwithout its use.

We claim:

1. An anhydrous, reversible lubricating grease composition consistingessentially of 50 to by weight, based on the total composition, of a lowcold test mineral oil thickened to a smooth homogeneous solid greasestructure with 10 to 50% of barium soap of fatty acid having 12 to 24carbon atoms, said barium soap having a pH value at least as low as 7.0and being prepared by dissolving said fatty acid in said mineral oil,adding an aqueous-oil slurry of carbonate-free barium hydroxide in notmore than stoichiometrical proportions, based on the fatty acid, andheating the ingredients to a temperature of about 200 F. to form bariumsoap in situ.

2. A reversible anhydrou lubricating grease composition consistingessentially of a mineral base lubricating oil thickened to a smoothhomogeneous solid grease consistency by 10 to 35% by weight, based onthe total composition,

"- of barium soap of aliphatic fatty acid having between about 12 andabout 24 carbon atoms, said soap havin a pH value at least as low as7.0, said soap being prepared by dissolving said fatty acid in said oil,adding not more than a theoretical quantity of a carbonate-free bariumhydroxide in an aqueous-oil slurry to saponify said acid, heating theingredients to a temperature of. about.200 F. to form the soap in situ,and thereafter heating to a temperature Within therange of about 275 to425 F. to remove water and leave a smooth grease structure.

3, A process for making a reversible lubricating grease compositionsubstantially free of soaps other than barium soap which consistingessentially of the steps of dissolving aliphatic fatty material havingbetween 12 and 24 carbon atoms per molecule in mineral lubricating oil,neutralizing said fatty material with not more than a stoichiometricalquantity of freshly hydrated barium oxide which is substantially free ofbarium carbonate, heating said composition to a temperature between 275F. and 425 F., and slowly cooling said composition to a soap formingtemperature of about 200 F., and thereafter removingwater by heatinfurther to substantially ambient temperature to obtain a smoothhomogeneous solid grease product having a pH value not greater than 7.0.

4. A process for preparing a reversible lubricating grease of bariumsoap and mineral lubricating 0 oil 'base substantially free of othersoaps, which consists essentially of calcining a barium-oxygen compoundcontaining CO2 to substantially remove said CO2 and leave asubstantially pure barium oxide, hydrating said oxide in a mannersubstantially to protect said oxide from contact with CO2, incorporatingsaid hydrate together with at least a theoretical proportion of C12 toC24 fatty acid in -mineral base lubricating oil, heating to an elevatedtemperature to form a nonbasic substantially pure barium soap in situ insaid oil, and slowly cooling the oil and soap mixture thereby forming astable smooth homogeneous solid grease structure.

5. A process for preparing a smooth solid homogeneous reversiblelubricating grease of barium soap and mineral oil base substantiallyfree of other soaps, which consists essentially of the steps of mixing asuflicient quantity of saponifi-' ARNOLD J. MORWAY. JOHN C. ZIMMER.

REFERENGES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,154,383 Ott et al Apr. 11, 19392,303,256 Camelford Nov. 24, 1942 2,332,247 Morway et al. Oct. 19, 19432,417,433 McLennan Mar. 18, 1947 2,434,539 Beerbower et a1. Jan. 13,1948 2,450,224 Bergmann et a1. Sept. 28, 1948 OTHER REFERENCES Boner:Metallic Soaps for Thickening Mineral Oils, article in Industrial andEngineering Chemistry, vol. 29, pp. 58, 59, and 60, Jan. 1937.

McLennan: Methods of Compounding Barium Greases, article in NationalPetroleum News, R-234, R-236, R-238, R-239, April 5, 1944.

1. AN ANHYDROUS, REVERSIBLE LUBRICATING GREASE COMPOSITION CONSISTINGESSENTIALLY OF 50 TO 90% BY WEIGHT, BASED ON THE TOTAL COMPOSITION, OF ALOW COLD TEST MINERAL OIL THICKENED TO A SMOOTH HOMOGENEOUS SOLID GREASESTRUCTURE WITH 10 TO 50% OF BARIUM SOAP OF FATTY ACID HAVING 12 TO 24CARBON ATOMS, SAID BARIUM SOAP HAVING A PH VALUE AT LEAST AS LOW AS 7.0AND BEING PREPARED BY DISSOLVING SAID FATTY ACID IN SAID MINERAL OIL,ADDING AN AQUEOUS-OIL SLURRY OF CARBONATE-FREE BARIUM HYDROXIDE IN NOTMORE THAN STOICHIOMETRICAL PROPORTIONS, BASED ON THE FATTY ACID, ANDHEATING THE INGREDIENTS TO A TEMPERATURE OF ABOUT 200*F. TO FORM BARIUMSOAP IN SITU.